Southern California experienced catastrophic wildfires in October 2007 that burned more than 500,000 acres and over 2,000 homes. Particulate matter (PM) concentrations were elevated for nearly two weeks, with 24- hour average PM10 and PM2.5 outdoor concentrations approaching 10 times the levels typically observed in some locations. During this wildfire period the Children's Health Study (CHS) field team was measuring lung function and exhaled NO (eNO), both objective measures of respiratory health, as part of previously scheduled activities. These concurrent events provide a unique opportunity to substantively improve current health risk assessment technology. By combining satellite imagery and remote sensing data with fixed-site monitoring data to produce local estimates of PM2.5 and PM10 exposure, our current health and exposure information can be used to improve wildfire event exposure assessment. For each day that the Southern California was impacted by recent wildfire smoke, the impact of smoke exposure on children's respiratory health can be assessed. Measurements of aerosol optical depth (AOD) made from MODIS (Moderate Resolution Imaging Spectroradiometer) will be integrated with satellite imagery, meteorological data, and fixed-site air pollution monitoring data to estimate PM concentrations for each one- to two-kilometer square grid cell in the air basin during the hours of elevated air pollution associated with the wildfire. We will examine whether estimated PM concentrations correlate with reported smoke exposures from a sample of over 500 CHS participants and by reports obtained from community public schools. Our unique cohort resource will be used to examine whether temporally- and spatially-resolved estimates of PM2.5 and PM10 concentrations during wildfires have short- (days) or longer-term (weeks or months) effects on children's lung function and eNO. The tools developed during this study will fill critical gaps in existing exposure assessment methods during future wildfire events, which are expected to recur and increase if potential global warming scenarios develop. Improved assessment of smoke exposures and a greater understanding of wildfire health effects will be important elements in making recommendations to protect public health during future wildfire events.